Inertia switches provide a means for detecting changes in axial or lateral forces. Some currently available inertia switch includes acceleration switches, which, as the name implies, are responsive to acceleration. Typically, an acceleration switch includes a system whereby a mass moves relative to an internal sensing element in response to acceleration.
One specific type of acceleration switch includes a mass-spring system having a mass with a flat spring contact secured thereto, the mass being biased in an open or closed position with respect to a conductive lead wire. The mass may be biased through use of a spring that provides a predetermined spring bias. When sufficient axial or lateral forces are applied to overcome the spring bias, the mass moves relative to the conductive lead wire. The movement of the mass separates the flat spring contact from, or brings the flat spring contact into contact with, the conductive lead wire to open or close the switch, respectively. Often, the flat spring contact is pressed into the mass with an interference fit for retention and electrical conductivity. However, the interference fit causes undue stress on the thin spring contact which results in various deformations, adversely affecting the function of the switch.
Additionally, current mass-spring systems utilize a manually-operated arbor tool to press the flat spring contact into the mass, which results in deformation to the spring contact from the high forces required to overcome the interference between the spring contact and the mass. This deformation may cause dimensional changes to the interface between the spring and the spring contact, adversely affecting the function of the switch.
Furthermore, current spring contact manufacturing includes forming a large number of individual spring contacts on a sheet of spring contact material. A break-off tab is provided for separating each spring contact from the sheet. As shown in FIG. 1, this break-off tab results in a protruding section of the spring contact which scrapes the inside of the mass during the insertion process, resulting in contact deformation. The interference press fit also creates particulate from the spring contact shaving material from the mass. This particulate may cause additional deformation to the spring contact, increasing the friction of the mass movement, and changing the electrical characteristics of the switch; all of which adversely affect the function of the switch.
A spring contact implemented in an inertia switch, and method of manufacturing an inertia switch with improvements in the process and/or the properties of the components formed would be desirable in the art.